docs: def _collectAxisPoints(self):
          """
              Return a dictionary with all on-axis locations.
          """
          for l, (value, deltaName) in self.items():
              location = Location(l)
              name = location.isOnAxis()
              if name is not None and name is not False:
                  if name not in self._axes:
                      self._axes[name] = []
                  if l not in self._axes[name]:
                      self._axes[name].append(l)
          return self._axes